When my SO and I started going out, my period were regular, but we were never intimate in any way. And just recently, due to starting high school, we've decided to get intimate. After my last period, we planned on having sex sometime between that one and this one, though we ended up not getting to. My periods are always regular, but once we decided this, I was late by almost two months. Would these have any correlation to each other? Or is it just a coincidence?